FEATURE: maybe have a configurable option not to send '0' values

[F1 Outsourcing Development]

There is a lot of 0 reported, maybe it is good not to log them since reporting/graphing tools already have a previous 0 option when there is no sample. Saves in my case 30% every scrape.

[@~]# grep ' 0$' exporter-output | wc -l
2276
[@~]# wc -l exporter-output
7766 exporter-output